HumanPen is a document-level AI humanizer that rewrites AI-flagged writing while keeping the document itself intact. Upload a DOCX, PPTX or TXT file of any length, and the tool rewrites only the passages that need it, preserving the exact layout, tables, numbering, citations, numbers, units, formulas and terminology, and the strength of each claim, without introducing deliberate typos or grammar errors to fool detectors. You can select passages yourself or import an existing Turnitin or iThenticate AI report to pinpoint exactly what was flagged, and you are charged only for the words actually rewritten, at 100 credits per 1,000 words. If a re-check still shows 20 percent or higher, the remaining flagged passages are rewritten for free until the score drops below 20 percent. The same platform also converts citation formats, shortens documents to a target length and translates files with the layout intact, and it plugs into AI agents through a skill, MCP server and API. Registering brings 100 free credits. It is built for students, researchers and professionals whose documents must read naturally while surviving detection checks with their formatting and evidence untouched.